In vivo biodistribution of mixed shell micelles with tunable hydrophilic/hydrophobic surface

A Dual-Channel Ca2+ Nanomodulator Induces Intracellular Ca2+ Disorders via Endogenous Ca2+ Redistribution for Tumor Radiosensitization

Tumor cells harness Ca2+ to maintain cellular homeostasis and withstand external stresses from various treatments. Here, a dual-channel Ca2+ nanomodulator (CAP-P-NO) is constructed that can induce irreversible intracellular Ca2+ disorders via the redistribution of tumor-inherent Ca2+ for disrupting cellular homeostasis and thus improving tumor radiosensitivity. Stimulated by tumor-overexpressed acid and glutathione, capsaicin and nitric oxide are successively escaped from CAP-P-NO to activate the transient receptor potential cation channel subfamily V member 1 and the ryanodine receptor for the influx of extracellular Ca2+ and the release of Ca2+ in the endoplasmic reticulum, respectively. The overwhelming level of Ca2+ in tumor cells not only impairs the function of organelles but also induces widespread changes in the gene transcriptome, including the downregulation of a set of radioresistance-associated genes. Combining CAP-P-NO treatment with radiotherapy achieves a significant suppression against both pancreatic and patient-derived hepatic tumors with negligible side effects. Together, the study provides a feasible approach for inducing tumor-specific intracellular Ca2+ overload via endogenous Ca2+ redistribution and demonstrates the great potential of Ca2+ disorder therapy in enhancing the sensitivity for tumor radiotherapy.

Nano-engineering nanomedicines with customized functions for tumor treatment applications

Nano-engineering with unique "custom function" capability has shown great potential in solving technical difficulties of nanomaterials in tumor treatment. Through tuning the size and surface properties controllablly, nanoparticles can be endoewd with tailored structure, and then the characteristic functions to improve the therapeutic effect of nanomedicines. Based on nano-engineering, many have been carried out to advance nano-engineering nanomedicine. In this review, the main research related to cancer therapy attached to the development of nanoengineering nanomedicines has been presented as follows. Firstly, therapeutic agents that target to tumor area can exert the therapeutic effect effectively. Secondly, drug resistance of tumor cells can be overcome to enhance the efficacy. Thirdly, remodeling the immunosuppressive microenvironment makes the therapeutic agents work with the autoimmune system to eliminate the primary tumor and then prevent tumor recurrence and metastasis. Finally, the development prospects of nano-engineering nanomedicine are also outlined.

Synergy between pH- and hypoxia-responsiveness in antibiotic-loaded micelles for eradicating mature, infectious biofilms

Antibiotic-loaded PEG/PAE-based micelles are frequently considered for eradicating infectious biofilms. At physiological pH, PEG facilitates transport through blood. Near an acidic infection-site, PAE becomes protonated causing micellar targeting to a biofilm. However, micellar penetration and accumulation is confined to the surface region of a biofilm. Especially matured biofilms also possess hypoxic regions. We here designed dual-responsive PEG/PAE-b-P(Lys-NBCF) micelles, responding to both acidity and low oxygen-saturation level in matured biofilms. Dual, pH- and hypoxia-responsive micelles targeted and accumulated evenly over the depth of 7- to 14-days old biofilms. Delineation demonstrated that pH-responsiveness was responsible for targeting of the infection-site and accumulation of micelles in the surface region of the biofilm. Hypoxia-responsiveness caused deep penetration in the biofilm. Dual, pH- and hypoxia-responsive micelles loaded with ciprofloxacin yielded more effective, synergistic eradication of 10-days old, matured Staphylococcus aureus biofilms underneath an abdominal imaging-window in living mice than achieved by ciprofloxacin in solution or single, pH- or hypoxia responsive micelles loaded with ciprofloxacin. Also, wound-healing after removal of window and its frame proceeded fastest after tail-vein injection of ciprofloxacin-loaded, dual, pH- and hypoxia-responsive micelles. Concluding, pH- and hypoxia-responsiveness are both required for eradicating mature biofilms and advancing responsive antibiotic nanocarriers to clinical application. STATEMENT OF SIGNIFICANCE: pH-responsive antibiotic nanocarriers have emerged as a possible new strategy to prevent antimicrobial-resistant bacterial infections from becoming the leading cause of death. In this paper, we show that commonly studied, pH-responsive micellar nanocarriers merely allow self-targeting to an infectious biofilm, but do not penetrate deeply into the biofilm. The dual-responsive (acidic pH- and hypoxia) antibiotic-loaded micelles designed here not only self-target to an infectious biofilm, but also penetrate deeply. The in vitro and in vivo advantages of dual-responsive nanocarriers are most obvious when studied in infectious biofilms grown for 10 viz a viz the 2 days, usually applied in the literature. Significantly, clinical treatment of bacterial infection usually starts more than 2 days after appearance of the first symptoms.

Tumor-Targeted Injectable Double-Network Hydrogel for Prevention of Breast Cancer Recurrence and Wound Infection via Synergistic Photothermal and Brachytherapy

The high locoregional recurrence rate and potential wound infection in breast cancer after surgery pose enormous risks to patient survival. In this study, a polyethylene glycol acrylate (PEGDA)-alginate double-network nanocomposite hydrogel (GPA) embedded with 125 I-labeled RGDY peptide-modified gold nanorods (125 I-GNR-RGDY) is fabricated. The double-network hydrogel is formed by injection of GPA precursor solutions into the cavity of resected cancerous breasts of mice where gelation occurred rapidly. The enhanced temperature-induced PEGDA polymerization driven by near-infrared light irradiation, and then, the second polymer network is crosslinked between alginate and endogenous Ca2+ around the tumor. The double-network hydrogel possesses a dense polymer network and tightly fixes 125 I-GNR-RGDY, which exhibit superior persistent photothermal and radioactive effects. Hyperthermia induced by photothermal therapy can inhibit self-repair of damaged DNA and promote blood circulation to improve the hypoxic microenvironment, which can synergistically enhance the therapeutic efficacy of brachytherapy and simultaneously eliminate pathogenic bacteria. Notably, this nanocomposite hydrogel facilitates antibacterial activity to prevent potential wound infection and is tracked by single-photon emission computerized tomography imaging owing to isotope labeling of loaded 125 I-GNR-RGDY. The combination of photothermal therapy and brachytherapy has enabled the possibility of proposing a novel postoperative adjuvant strategy for preventing tumor recurrence and wound infection.

α-Amino acid N-carboxyanhydride (NCA)-derived synthetic polypeptides for nucleic acids delivery

In recent years, gene therapy has come into the spotlight for the prevention and treatment of a wide range of diseases. Polypeptides have been widely used in mediating nucleic acid delivery, due to their versatilities in chemical structures, desired biodegradability, and low cytotoxicity. Chemistry plays an essential role in the development of innovative polypeptides to address the challenges of producing efficient and safe gene vectors. In this Review, we mainly focused on the latest chemical advances in the design and preparation of polypeptide-based nucleic acid delivery vehicles. We first discussed the synthetic approach of polypeptides via ring-opening polymerization (ROP) of N-carboxyanhydrides (NCAs), and introduced the various types of polypeptide-based gene delivery systems. The extracellular and intracellular barriers against nucleic acid delivery were then outlined, followed by detailed review on the recent advances in polypeptide-based delivery systems that can overcome these barriers to enable in vitro and in vivo gene transfection. Finally, we concluded this review with perspectives in this field.

Absorption, distribution, metabolism, and excretion of nanocarriers in vivo and their influences

As one of the most promising and effective delivery systems for targeted controlled-release drugs, nanocarriers (NCs) have been widely studied. Although the development of nanoparticle preparations is very prosperous, the safety and effectiveness of NCs are not guaranteed and cannot be precisely controlled due to the unclear processes of absorption, distribution, metabolism, and excretion (ADME), as well as the drug release mechanism of NCs in the body. Thus, the approval of NCs for clinical use is extremely rare. This paper reviews the research progress and challenges of using NCs in vivo based on a review of several hundred closely related publications. First, the ADME of NCs under different administration routes is summarized; second, the influences of the physical, chemical, and biosensitive properties, as well as targeted modifications of NCs on their disposal process, are systematically analyzed; third, the tracer technology related to the in vivo study of NCs is elaborated; and finally, the challenges and perspectives of nanoparticle research in vivo are introduced. This review may help readers to understand the current research progress and challenges of nanoparticles in vivo, as well as of tracing technology in nanoparticle research, to help researchers to design safer and more efficient NCs. Furthermore, this review may aid researchers in choosing or exploring more suitable tracing technologies to further advance the development of nanotechnology.

Dual-responsive doxorubicin-loaded nanomicelles for enhanced cancer therapy

BACKGROUND

The enhancement of tumor retention and cellular uptake of drugs are important factors in maximizing anticancer therapy and minimizing side effects of encapsulated drugs. Herein, a delivery nanoplatform, armed with a pH-triggered charge-reversal capability and self-amplifiable reactive oxygen species (ROS)-induced drug release, is constructed by encapsulating doxorubicin (DOX) in pH/ROS-responsive polymeric micelle.

RESULTS

The surface charge of this system was converted from negative to positive from pH 7.4 to pH 6.8, which facilitated the cellular uptake. In addition, methionine-based system was dissociated in a ROS-rich and acidic intracellular environment, resulting in the release of DOX and α-tocopheryl succinate (TOS). Then, the exposed TOS segments further induced the generation of ROS, leading to self-amplifiable disassembly of the micelles and drug release.

CONCLUSIONS

We confirms efficient DOX delivery into cancer cells, upregulation of tumoral ROS level and induction of the apoptotic capability in vitro. The system exhibits outstanding tumor inhibition capability in vivo, indicating that dual stimuli nano-system has great potential to function as an anticancer drug delivery platform.

Morphological Transitions in Patchy Nanoparticles

Nanoparticles (NPs) decorated with topographically or chemically distinct surface patches are an emerging class of colloidal building blocks of functional hierarchical materials. Surface segregation of polymer ligands into pinned micelles offers a strategy for the generation of patchy NPs with controlled spatial distribution and number of patches. The thermodynamic nature of this approach poses a question about the stability of multiple patches on the NP surface, as the lowest energy state is expected for NPs carrying a single patch. In the present work, for gold NPs end-grafted with thiol-terminated polymer molecules, we show that the patchy surface morphology is preserved under conditions of strong grafting of the thiol groups to the NP surface (i.e., up to a temperature of 40 °C), although the patch shape changes over time. At higher temperatures (e.g., at 80 °C), the number of patches per NP decreases, due to the increased lateral mobility and coalescence of the patches as well as the ultimate loss of the polymer ligands due to desorption at enhanced solvent quality. The experimental results were rationalized theoretically, using a scaling approach. The results of this work offer insight into the surface science of patchy nanocolloids and specify the time and temperature ranges of the applications of patchy NPs.

Precise regulation of particle size of poly(N-isopropylacrylamide) microgels: Measuring chain dimensions with a "molecular ruler"

HYPOTHESIS

Poly(N-isopropylacrylamide) microgels are used extensively in the design of drug carriers, surfaces for control of cell adhesion, and optical devices. Particle size is a key factor and has a significant influence in many areas.

EXPERIMENTS

In this work, precise control of the particle size of poly(N-isopropylacrylamide) microgels was achieved by controlling the separation distance of the poly(N-isopropylacrylamide) chains. Dibromoalkanes of different size were used as an adjustable "molecular ruler" to measure molecular dimensions in poly(N-isopropylacrylamide) nanoaggregates at the critical crosslinking temperature.

FINDINGS

We find that the chain separation distance decreases as the temperature increases with a sharp decrease over the 55-to-65 °C interval. Based on the observed relationships between chain separation and crosslinker, the particle size of poly(N-isopropylacrylamide) microgels can be regulated by changing the length of the "molecular ruler" (crosslinker) at the same temperature. Furthermore, for partly crosslinked poly(N-isopropylacrylamide) microgels that contain free crosslinkable sites, the particle size can be reduced still more by further crosslinking ("re-crosslinking") with crosslinkers of different size. It is shown that the particle size can be regulated by adjusting the length of "molecular ruler" and the degree of crosslinking. This work provides a "molecular level" method for precise control of poly(N-isopropylacrylamide) microgel particle size.

ICG-Conjugated and 125 I-Labeled Polymeric Micelles with High Biosafety for Multimodality Imaging-Guided Photothermal Therapy of Tumors

Noninvasive multimodality imaging-guided precision photothermal therapy (PTT) is proven to be an effective strategy for tumor theranostics by integrating diagnostics and therapeutics in one nanoplatform. In this study, indocyanine green (ICG)-conjugated and radionuclide iodine-125 (125 I)-labeled polymeric micelles (PEG-PTyr(125 I)-ICG PMs) are strategically prepared by the self-assembly of the ICG-decorated amphiphilic diblock polymer poly(ethylene glycol)-poly(l-tyrosine-125 I)-(indocyanine green) (PEG-PTyr(125 I)-ICG). The as-prepared polymeric micelles exhibit favorable biocompatibility, excellent size/photo/radiolabel stability, a high-photothermal conversion efficiency, a passive tumor-targeting ability, and a fluorescence (FL)/photoacoustic (PA)/single photon emission computed tomography (SPECT) imaging property. After tail intravenous injection, the polymeric micelles can efficiently accumulate at the tumor site and present comprehensive FL/PA/SPECT images with a high sensitivity, excellent spatial resolution, and unlimited tissue penetration under near-infrared (NIR) irradiation. Upon 808 nm laser irradiation, the subsequent precision PTT of tumors can be achieved with minimal cumulative side effects. Thus, this capable multifunctional nanoplatform with simple components and preparation procedures for FL/PA/SPECT multimodality imaging-guided PTT can be a potential candidate for clinical tumor theranostics.

Heat Shock Protein Inspired Nanochaperones Restore Amyloid-β Homeostasis for Preventative Therapy of Alzheimer's Disease

Amyloid beta (Aβ) aggregation is generally believed as the crucial and primary cause of Alzheimer's disease (AD). However, current Aβ-targeted therapeutic strategies show limited disease-modifying efficacy due to the irreversible damages in the late stage of AD, thus the treatment should be given before the formation of deposition and target primary Aβ species rather than advanced plaques. Herein, inspired by heat shock protein, a self-assembly nanochaperone based on mixed-shell polymeric micelle (MSPM) is devised to act as a novel strategy for AD prevention. With unique surface hydrophobic domains, this nanochaperone can selectively capture Aβ peptides, effectively suppress Aβ aggregation, and remarkably reduce Aβ-mediated cytotoxicity. Moreover, the formed nanochaperone-Aβ complex after Aβ adsorption can be easily phagocytosed by microglia and thereby facilitates Aβ clearance. As a result, the nanochaperone reduces Aβ burden, attenuates Aβ-induced inflammation, and eventually rescues the cognitive deficits of APP/PS1 transgenic AD mice. These results indicate that this biomimetic nanochaperone can successfully prevent the onset of AD symptoms and serve as a promising candidate for prophylactic treatment of AD.

Physicochemical, Pharmacokinetic, and Toxicity Evaluation of Methoxy Poly(ethylene glycol)-b-Poly(d,l-Lactide) Polymeric Micelles Encapsulating Alpinumisoflavone Extracted from Unripe Cudrania tricuspidata Fruit

Alpinumisoflavone, a major compound in unripe Cudrania tricuspidata fruit is reported to exhibit numerous beneficial pharmacological activities, such as osteoprotective, antibacterial, estrogenic, anti-metastatic, atheroprotective, antioxidant, and anticancer effects. Despite its medicinal value, alpinumisoflavone is poorly soluble in water, which makes it difficult to formulate and administer intravenously (i.v.). To overcome these limitations, we used methoxy poly(ethylene glycol)-b-poly(d,l-lactide) (mPEG-b-PLA) polymeric micelles to solubilize alpinumisoflavone and increase its bioavailability, and evaluated their toxicity in vivo. Alpinumisoflavone-loaded polymeric micelles were prepared using thin-film hydration method, and their physicochemical properties were characterized for drug release, particle size, drug-loading (DL, %), and encapsulation efficiency (EE, %). The in vitro drug release profile was determined and the release rate of alpinumisoflavone from mPEG-b-PLA micelles was slower than that from drug solution, and sustained. Pharmacokinetic studies showed decreased total clearance and volume of distribution of alpinumisoflavone, whereas area under the curve (AUC) and bioavailability were significantly increased by incorporation in mPEG-b-PLA micelles. In vivo toxicity assay revealed that alpinumisoflavone-loaded mPEG-b-PLA micelles had no severe toxicity. In conclusion, we prepared an intravenous (i.v.) injectable alpinumisoflavone formulation, which was solubilized using mPEG-b-PLA micelles, and determined their physicochemical properties, pharmacokinetics, and toxicity profiles.

Transforming stealthy to sticky nanocarriers: a potential application for tumor therapy

Nanomedicine has shown remarkable progress in preclinical studies of tumor treatment. Over the past decade, scientists have developed various nanocarriers (NCs) for delivering drugs into the tumor area. However, the average amount of accumulated drugs in tumor sites is far from satisfactory. This limitation is strongly related to the corona formation during blood circulation. To overcome this issue, NCs should be designed to become highly stealthy by modifying their surface charge. However, at the same time, stealthy effects not only prevent protein formation but also alleviate the cellular uptake of NCs. Therefore, it is necessary to develop NCs with switchable properties, which are stealthy in the circulation system and sticky when arriving at tumor sites. In this review, we discuss the recent strategies to develop passive and active charge-switchable NCs, known as chameleon-like drug delivery systems, which can reversibly transform their surface from stealthy to sticky and have various designs.

Recent Advances in Polymeric Nanomedicines for Cancer Immunotherapy

Immunotherapy has emerged as a promising approach to treat cancer, since it facilitates eradication of cancer by enhancing innate and/or adaptive immunity without using cytotoxic drugs. Of the immunotherapeutic approaches, significant clinical potentials are shown in cancer vaccination, immune checkpoint therapy, and adoptive cell transfer. Nevertheless, conventional immunotherapies often involve immune-related adverse effects, such as liver dysfunction, hypophysitis, type I diabetes, and neuropathy. In an attempt to address these issues, polymeric nanomedicines are extensively investigated in recent years. In this review, recent advances in polymeric nanomedicines for cancer immunotherapy are highlighted and thoroughly discussed in terms of 1) antigen presentation, 2) activation of antigen-presenting cells and T cells, and 3) promotion of effector cells. Also, the future perspectives to develop ideal nanomedicines for cancer immunotherapy are provided.

Nanoparticle heterogeneity: an emerging structural parameter influencing particle fate in biological media?

Drug nanocarriers' surface chemistry is often presumed to be uniform. For instance, the polymer surface coverage and distribution of ligands on nanoparticles are described with averaged values obtained from quantification techniques based on particle populations. However, these averaged values may conceal heterogeneities at different levels, either because of the presence of particle sub-populations or because of surface inhomogeneities, such as patchy surfaces on individual particles. The characterization and quantification of chemical surface heterogeneities are tedious tasks, which are rather limited by the currently available instruments and research protocols. However, heterogeneities may contribute to some non-linear effects observed during the nanoformulation optimization process, cause problems related to nanocarrier production scale-up and correlate with unexpected biological outcomes. On the other hand, heterogeneities, while usually unintended and detrimental to nanocarrier performance, may, in some cases, be sought as adjustable properties that provide NPs with unique functionality. In this review, results and processes related to this issue are compiled, and perspectives and possible analytical developments are discussed.

Ligand-Switchable Micellar Nanocarriers for Prolonging Circulation Time and Enhancing Targeting Efficiency

Targeted drug delivery of nanomedicines offered a promising strategy to improve the tumor accumulation and reduce the side effects of chemotherapeutics. However, undesired recognition of the targeting ligands on the surface of nanocarriers by immune systems or normal tissues decreased the circulation time and reduced the targeting efficiency. Here, we developed a ligand-switchable micellar nanocarrier that can hide the targeting ligands when circulating in the bloodstream and expose them on the surface when entering the tumor microenvironments. With the ligand-switching capability, the nanocarrier achieved a 66% longer blood circulation half-life and a 23% higher tumor accumulation than the nanocarrier with targeting ligands on the surface. This targeting strategy could serve as a universal approach to improve the targeting efficiency for nanomedicines.

Surface-adaptive zwitterionic nanoparticles for prolonged blood circulation time and enhanced cellular uptake in tumor cells

Recently, zwitterionic materials have been developed as alternatives to PEG for prolonging the circulation time of nanoparticles without triggering immune responses. However, zwitterionic coatings also hindered the interactions between nanoparticles and tumor cells, leading to less efficient uptake of nanoparticles by cancer cells. Such effect significantly limited the applications of zwitterionic materials for the purposes of drug delivery and the development to novel therapeutic agents. To overcome these issues, surface-adaptive mixed-shell micelles (MSMs) with poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC)/poly(β-amino ester) (PAE) heterogeneous surfaces were constructed. Owing to the synergistic effect of zwitterionic coatings and micro-phase-separated surfaces, PMPC mixed-shell micelles exhibited the improved blood circulation time compared to single-PEG-shell micelles (PEGSMs) and single-PMPC-shell micelles (PMPCSMs). Moreover, such MSMs can convert their surface to positively charged ones in response to the acidic tumor microenvironment, leading to a significant enhancement in cellular uptake of MSMs by tumor cells. This strategy demonstrated a general approach to enhance the cellular uptake of zwitterionic nanoparticles without compromising their long circulating capability, providing a practical method for improving the tumor-targeting efficiency of particulate drug delivery systems.

STATEMENT OF SIGNIFICANCE

Herein we demonstrate a general strategy to integrate non-fouling zwitterionic surface on the nanoparticles without compromising their capability of tumor accumulation, by constructing a surface-adaptive mixed-shell micelles (MSMs) with poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC)/poly(β-amino ester) (PAE) heterogeneous surfaces. At the blood pH (7.4), PAE chains collapsed to the inner of the shell due to the deprotonation, and the forming micro-phase separation structure was synergistic with zwitterionic surface to prolong the circulation time of MSMs in the blood. While at the tumor sites, PAE was protonated, and the positively charged surface of MSMs enhanced cellular uptake. This self-assembly-based strategy is compatible to other zwitterionic materials, endowing a great flexibility for the construction of responsive drug delivery systems particularly to the novel chemotherapeutic agents.

A mobile precursor determines protein resistance on nanostructured surfaces

A 2D-mobile protein in a precursor state is a prerequisite to protein resistance on nanostructured surfaces.

Compact Vesicles Self-Assembled from Binary Graft Copolymers with High Hydrophilic Fraction for Potential Drug/Protein Delivery

Hollow vesicles self-assembled from amphiphilic copolymers are of great interest in biomedicine field as drug and protein carriers. Efficient preparation of polymeric vesicles with high stability in vivo is highly desirable. Herein, a novel cooperative self-assembly of two graft copolymers (GCPs) with reversed hydrophilic-hydrophobic segments is investigated to achieve morphology control for biomedical application. Interestingly, nanosized vesicles are obtained for the binary system with relatively high hydrophilic fraction (f_hydrophilic, ∼60%), contrary to what is found in its single-component counterpart. The cooperative self-assembly endowed the hybrid vesicles with excellent resistance to protein adsorption, prolonged blood circulation time, as well as low leakage of hydrophilic drugs/proteins. Furthermore, the biological activity of the protein is well preserved inside the cooperative vesicles, making it a promising candidate as the protein carrier.

Electrostatic interactions between polyglutamic acid and polylysine yields stable polyion complex micelles for deoxypodophyllotoxin delivery

To achieve enhanced physical stability of poly(ethylene glycol)-poly(d,l-lactide) polymeric micelles (PEG-PDLLA PMs), a mixture of methoxy PEG-PDLLA-polyglutamate (mPEG-PDLLA-PLG) and mPEG-PDLLA-poly(l-lysine) (mPEG-PDLLA-PLL) copolymers was applied to self-assembled stable micelles with polyion-stabilized cores. Prior to micelle preparation, the synthetic copolymers were characterized by 1H-nuclear magnetic resonance (NMR) and infrared spectroscopy (IR), and their molecular weights were calculated by 1H-NMR and gel permeation chromatography (GPC). Dialysis was used to prepare PMs with deoxypodophyllotoxin (DPT). Transmission electron microscopy (TEM) images showed that DPT polyion complex micelles (DPT-PCMs) were spherical, with uniform distribution and particle sizes of 36.3±0.8 nm. In addition, compared with nonpeptide-modified DPT-PMs, the stability of DPT-PCMs was significantly improved under various temperatures. In the meantime, the pH sensitivity induced by charged peptides allowed them to have a stronger antitumor effect and a pH-triggered release profile. As a result, the dynamic characteristic of DPT-PCM was retained, and high biocompatibility of DPT-PCM was observed in an in vivo study. These results indicated that the interaction of anionic and cationic charged polyionic segments could be an effective strategy to control drug release and to improve the stability of polymer-based nanocarriers.

Micelles Formed by Polypeptide Containing Polymers Synthesized Via N-Carboxy Anhydrides and Their Application for Cancer Treatment

The development of multifunctional polymeric materials for biological applications is mainly guided by the goal of achieving the encapsulation of pharmaceutical compounds through a self-assembly process to form nanoconstructs that control the biodistribution of the active compounds, and therefore minimize systemic side effects. Micelles are formed from amphiphilic polymers in a selective solvent. In biological applications, micelles are formed in water, and their cores are loaded with hydrophobic pharmaceutics, where they are solubilized and are usually delivered through the blood compartment. Even though a large number of polymeric materials that form nanocarrier delivery systems has been investigated, a surprisingly small subset of these technologies has demonstrated potentially curative preclinical results, and fewer have progressed towards commercialization. One of the most promising classes of polymeric materials for drug delivery applications is polypeptides, which combine the properties of the conventional polymers with the 3D structure of natural proteins, i.e., α-helices and β-sheets. In this article, the synthetic pathways followed to develop well-defined polymeric micelles based on polypeptides prepared through ring-opening polymerization (ROP) of N-carboxy anhydrides are reviewed. Among these works, we focus on studies performed on micellar delivery systems to treat cancer. The review is limited to systems presented from 2000⁻2017.

Silver-Decorated Polymeric Micelles Combined with Curcumin for Enhanced Antibacterial Activity

Because of the mounting prevalence of complicated infections induced by multidrug-resistant bacteria, it is imperative to develop innovative and efficient antibacterial agents. In this work, we design a novel polymeric micelle for simultaneous decorating of silver nanoparticles and encapsulating of curcumin as a combination strategy to improve the antibacterial efficiency. In the constructed combination system, silver nanoparticles were decorated in the micellar shell because of the in situ reduction of silver ions, which were absorbed by the poly(aspartic acid) (PAsp) chains in the shell. Meanwhile, natural curcumin was encapsulated into the poly(ε-caprolactone) (PCL) core of the micelle through hydrophobic interaction. This strategy could prevent aggregation of silver nanoparticles and improve the water solubility of curcumin at the same time, which showed enhanced antibacterial activity toward Gram-negative P.aeruginosa and Gram-positive S.aureus compared with sliver-decorated micelle and curcumin-loaded micelle alone, due to the cooperative antibacterial effects of the silver nanoparticles and curcumin. Furthermore, the achieved combinational micelles had good biocompatibility and low hemolytic activity. Thus, our study provides a new pathway in the rational design of combination strategy for efficiently preventing the ubiquitous bacterial infections.

A tumour microenvironment-responsive polymeric complex for targeted depletion of tumour-associated macrophages (TAMs)

A dual-level targeting polymeric system to eliminate tumour-associated macrophages.

Iminoboronate-based dual-responsive micelles via subcomponent self-assembly for hydrophilic 1,2-diol-containing drug delivery

Iminoboronate-based dual-responsive micelles were fabricated via simple subcomponent self-assembly for delivery of hydrophilic 1,2-diol-containing drugs.

Synergistic effects of negative-charged nanoparticles assisted by ultrasound on the reversal multidrug resistance phenotype in breast cancer cells

We have fabricated a negative-charged nanoparticle (Heparin-Folate-Tat-Taxol NP, H-F-Tat-T NP) with dual ligands, tumor targeting ligand folate and cell-penetrating peptide Tat, to deliver taxol presenting great anticancer activity for sensitive cancer cells, while it fails to overcome multidrug resistance (MDR) in MCF-7/T cells (taxol-resistant breast cancer cells). Ultrasound (US) can increase the sensitivity of positive-charged NPs thereby making it possible to reverse MDR through inducing NPs' drug release. However, compared with the negative-charged NPs, positive-charged NPs may cause higher toxic effect. Hence, the combination of negative-charged NPs and US may be an efficient strategy for overcoming MDR. The conventional procedure to treat with NPs followed by US exposure possibly destruct multifunctional NPs resulting in its bioactivity inhibition. Herein, we have further improved the operating approach to eliminate US mechanical damage and keep the integrity of negative-charged NPs: cells are exposed to US with microbubbles (MBs) prior to the treatment of H-F-Tat-T NPs. Superior to the conventional method, US sonoporation affects the physiological property of cancer cells while preventing direct promotion of drug release from NPs. The results of the present study displayed that US in condition (1MHz, 10% duty cycle, duration of 80s, US intensity of 0.6W/cm² and volume ratio of medium to MBs 20:1) combined with H-F-T-Tat-T NPs can achieve optimal reversal MDR effect in MCF-7/T cells. Mechanism study further disclosed that the individual effect of US was responsible for the enhancement of cell membrane permeability, inhibition of cell proliferation rate and down-regulation of MDR-related genes and proteins. Simultaneously, US sonoporation on resistant cancer cells indirectly increased the accumulation of NPs by inducing endosomal escape of negative-charged NPs. Taken together, the overcoming MDR ability for the combined strategy was achieved by the synergistic effect from individual function of NPs, physiological changes of resistant cancer cells and behavior changes of NPs caused by US.

CO2-Responsive graft copolymers: synthesis and characterization

The synthesis and self-assembly study of CO₂-responsive graft copolymers fabricated from a “graft-to” strategy based on pentafluorophenyl esters as grafting sites.

Facile fabrication of poly(acrylic acid) coated chitosan nanoparticles with improved stability in biological environments

Chitosan is one of the most important and commonly used natural polysaccharides in drug delivery for its biocompatible and biodegradable properties. However, poor blood circulation of the chitosan nanoparticles due to their cationic nature is one of the major bottlenecks of chitosan-based drug delivery systems. To address this problem, a versatile platform based on poly(acrylic acid) (PAA) coated ionically cross-linked chitosan/tripolyphosphate nanoparticles (CTS/TPP-PAA NPs), is reported. The zeta potentials of CTS/TPP and CTS/TPP-PAA NPs are approximately 33mV and -25mV, respectively. CTS/TPP NPs quickly aggregate in PBS (phosphate buffered saline) and DMEM (Dulbecco's modified Eagle's medium). Conversely, CTS/TPP-PAA NPs exhibit excellent colloidal stability in plasma solution for more than 24h. The PAA coating also endows CTS/TPP-PAA NPs with decreased protein adsorption capacity and improved buffering capacity. More importantly, the residual carboxyl and amino groups on CTS/TPP-PAA NPs provide abundant reactive sites for further functional modifications. Therefore, the CTS/TPP-PAA NPs reported here may be useful as an alternative drug delivery system.

Polymeric nanoparticles in development for treatment of pulmonary infectious diseases

Serious lung infections, such as pneumonia, tuberculosis, and chronic obstructive cystic fibrosis-related bacterial diseases, are increasingly difficult to treat and can be life-threatening. Over the last decades, an array of therapeutics and/or diagnostics have been exploited for management of pulmonary infections, but the advent of drug-resistant bacteria and the adverse conditions experienced upon reaching the lung environment urge the development of more effective delivery vehicles. Nanotechnology is revolutionizing the approach to circumventing these barriers, enabling better management of pulmonary infectious diseases. In particular, polymeric nanoparticle-based therapeutics have emerged as promising candidates, allowing for programmed design of multi-functional nanodevices and, subsequently, improved pharmacokinetics and therapeutic efficiency, as compared to conventional routes of delivery. Direct delivery to the lungs of such nanoparticles, loaded with appropriate antimicrobials and equipped with 'smart' features to overcome various mucosal and cellular barriers, is a promising approach to localize and concentrate therapeutics at the site of infection while minimizing systemic exposure to the therapeutic agents. The present review focuses on recent progress (2005-2015) important for the rational design of nanostructures, particularly polymeric nanoparticles, for the treatment of pulmonary infections with highlights on the influences of size, shape, composition, and surface characteristics of antimicrobial-bearing polymeric nanoparticles on their biodistribution, therapeutic efficacy, and toxicity. WIREs Nanomed Nanobiotechnol 2016, 8:842-871. doi: 10.1002/wnan.1401 For further resources related to this article, please visit the WIREs website.

Effect of the Surface Charge of Artificial Chaperones on the Refolding of Thermally Denatured Lysozymes

Artificial chaperones are of great interest in fighting protein misfolding and aggregation for the protection of protein bioactivity. A comprehensive understanding of the interaction between artificial chaperones and proteins is critical for the effective utilization of these materials in biomedicine. In this work, we fabricated three kinds of artificial chaperones with different surface charges based on mixed-shell polymeric micelles (MSPMs), and investigated their protective effect for lysozymes under thermal stress. It was found that MSPMs with different surface charges showed distinct chaperone-like behavior, and the neutral MSPM with PEG shell and PMEO2MA hydrophobic domain at high temperature is superior to the negatively and positively charged one, because of the excessive electrostatic interactions between the protein and charged MSPMs. The results may benefit to optimize this kind of artificial chaperone with enhanced properties and expand their application in the future.

Heterogeneous surfaces to repel proteins

The nonspecific adsorption of proteins is usually undesirable on solid surfaces as it induces adverse responses, such as platelet adhesion on medical devices, negative signals of biosensors and contamination blockage of filtration membranes. Thus, an important scheme in material science is to design and fabricate protein-repulsive surfaces. Early approaches in this field focused on homogeneous surfaces comprised of single type functionality. Yet, recent researches have demonstrated that surfaces with heterogeneities (chemistry and topography) show promising performance against protein adsorption. In this review, we will summarize the recent achievements and discuss the new perspectives in the research of developing and characterizing heterogeneous surfaces to repel proteins. The protein repulsion mechanisms of different heterogeneous surfaces will also be discussed in details, followed by the perspective and challenge of this emerging field.

Fabrication of thermo-sensitive complex micelles for reversible cell targeting

To ideally solve the contradiction between enhanced cellular uptake and prolonged blood circulation, reversible targeting polymeric micelles based on the expanding and shrinking behavior of a temperature-responsive polymer were developed. The micelle contained a hydrophobic PCL core and a mixed shell consisting of poly(N-isopropylacrylamide) (PNIPAAm) and biotin-terminated poly(ethylene glycol) (Biotin-PEG), and its targeting ability could be switched on/off by temperature. The cellular uptake of the complex polymeric micelles was studied. The results from a quantitative enzyme-linked immunosorbent assay (ELISA) indicated that the surface biotin content increased by as much as 11.6-fold when the temperature increased above the lower critical solution temperature (LCST). More importantly, the ELISA confirmed that biotin-mediated targeting on the surface was reversibly switched on and off for at least five cycles. In addition, the results from quantitative flow cytometry and confocal spectroscopy indicated that the cellular uptake of the targeted micelles at temperatures above the LCST was much higher than that at temperatures below the LCST. This complex polymeric micelle with reversible targeting property could be a promising alternative for drug delivery.

Artificial chaperones based on mixed shell polymeric micelles: insight into the mechanism of the interaction of the chaperone with substrate proteins using Förster resonance energy transfer

Controlled and reversible interactions between polymeric nanoparticles and proteins have gained more and more attention with the hope to address many biological issues such as prevention of protein denaturation, interference of the fibrillation of disease relative proteins, removing of toxic biomolecules as well as targeting delivery of proteins, etc. In such cases, proper analytic techniques are needed to reveal the underlying mechanism of the particle-protein interactions. In the current work, Förster Resonance Energy Transfer (FRET) was used to investigate the interaction of our tailor designed artificial chaperone based on mixed shell polymeric micelles (MSPMs) with their substrate proteins. We designed a new kind of MSPMs with fluorescent acceptors precisely placed at the desired locations as well as hydrophobic domains which can adsorb unfolded proteins with a propensity to aggregate. Interactions of such model micelles with a donor-labeled protein-FITC-lysozyme, was monitored by FRET. The fabrication strategy of MSPMs makes it possible to control the accurate location of the acceptor, which is critical to reveal some unexpected insights of the micelle-protein interactions upon heating and cooling. Preadsorption of native proteins onto the hydrophobic domains of the MSPMs is a key step to prevent thermo-denaturation by diminishing interprotein aggregations. Reversible protein adsorption during heating and releasing during cooling have been confirmed. Conclusions from the FRET effect are in line with the measurement of residual enzymatic activity.

Ternary polyplex micelles with PEG shells and intermediate barrier to complexed DNA cores for efficient systemic gene delivery

Simultaneous achievement of prolonged retention in blood circulation and efficient gene transfection activity in target tissues has always been a major challenge hindering in vivo applications of nonviral gene vectors via systemic administration. Herein, we constructed novel rod-shaped ternary polyplex micelles (TPMs) via complexation between the mixed block copolymers of poly(ethylene glycol)-b-poly{N'-[N-(2-aminoethyl)-2-aminoethyl]aspartamide} (PEG-b-PAsp(DET)) and poly(N-isopropylacrylamide)-b-PAsp(DET) (PNIPAM-b-PAsp(DET)) and plasmid DNA (pDNA) at room temperature, exhibiting distinct temperature-responsive formation of a hydrophobic intermediate layer between PEG shells and pDNA cores through facile temperature increase from room temperature to body temperature (~37 °C). As compared with binary polyplex micelles of PEG-b-PAsp(DET) (BPMs), TPMs were confirmed to condense pDNA into a more compact structure, which achieved enhanced tolerability to nuclease digestion and strong counter polyanion exchange. In vitro gene transfection results demonstrated TPMs exhibiting enhanced gene transfection efficiency due to efficient cellular uptake and endosomal escape. Moreover, in vivo performance evaluation after intravenous injection confirmed that TPMs achieved significantly prolonged blood circulation, high tumor accumulation, and promoted gene expression in tumor tissue. Moreover, TPMs loading therapeutic pDNA encoding an anti-angiogenic protein remarkably suppressed tumor growth following intravenous injection into H22 tumor-bearing mice. These results suggest TPMs with PEG shells and facilely engineered intermediate barrier to inner complexed pDNA have great potentials as systemic nonviral gene vectors for cancer gene therapy.

Gene therapy for nucleus pulposus regeneration by heme oxygenase-1 plasmid DNA carried by mixed polyplex micelles with thermo-responsive heterogeneous coronas

Safe and high-efficiency gene therapy for nucleus pulposus (NP) regeneration was urgently desired to treat disc degeneration-associated diseases. In this work, an efficient nonviral cationic block copolymer gene delivery system was used to deliver therapeutic plasmid DNA (pDNA), which was prepared via complexation between the mixed cationic block copolymers, poly(ethylene glycol)-block-poly{N-[N-(2-aminoethyl)-2-aminoehtyl]aspartamide} [PEG-b-PAsp(DET)] and poly(N-isopropylacrylamide)-block-PAsp(DET) [PNIPAM-b-PAsp(DET)], and pDNA at 25 °C. The mixed polyplex micelles (MPMs) containing heterogeneous coronas with hydrophobic and hydrophilic microdomains coexisting could be obtained upon heating from 25 to 37 °C, which showed high tolerability against nuclease and strong resistance towards protein adsorption. The gene transfection efficiency of MPMs in NP cells was significantly higher than that of regular polyplex micelles prepared from sole block copolymer of PEG-b-PAsp(DET) (SPMs) in in vitro and in vivo evaluation due to the synergistic effect of improved colloidal stability and low cytotoxicity. High expression of heme oxygenase-1 (HO-1) in NP cells transfected by MPMs loading HO-1 pDNA significantly decreased the expression activity of matrix metalloproteinases 3 (MMP-3) and cyclo-oxygenase-2 (COX-2) induced by interleukin-1β (IL-1β), and simultaneously increased the NP phenotype-associated genes such as aggrecan, type II collagen, and SOX-9. Moreover, the therapeutic effects of MPMs loading pDNA were tested to treat disc degeneration induced by stab injury. The results demonstrated that administration of HO-1 pDNA carried by MPMs in rat tail discs apparently reduced inflammatory responses induced by need stab and increased glycosaminoglycan (GAG) content, finally achieving better therapeutic efficacy as compared with SPMs. Consequently, MPMs loading HO-1 pDNA were demonstrated to be potential as a safe and high-efficiency nonviral gene delivery system for retarding or regenerating the degenerative discs.

In vivo evaluation of folate decorated cross-linked micelles for the delivery of platinum anticancer drugs

The biodistribution of micelles with and without folic acid targeting ligands were studied using a block copolymer consisting of acrylic acid (AA) and polyethylene glycol methyl ether acrylate (PEGMEA) blocks. The polymers were prepared using RAFT polymerization in the presence of a folic acid functionalized RAFT agent. Oxoplatin was conjugated onto the acrylic acid block to form amphiphilic polymers which, when diluted in water, formed stable micelles. In order to probe the in vivo stability, a selection of micelles were cross-linked using 1,8-diamino octane. The sizes of the micelles used in this study range between 75 and 200 nm, with both spherical and worm-like conformation. The effects of cross-linking, folate conjugation and different conformation on the biodistribution were studied in female nude mice (BALB/c) following intravenous injection into the tail vein. Using optical imaging to monitor the fluorophore-labeled polymer, the in vivo biodistribution of the micelles was monitored over a 48 h time-course after which the organs were removed and evaluated ex vivo. These experiments showed that both cross-linking and conjugation with folic acid led to increased fluorescence intensities in the organs, especially in the liver and kidneys, while micelles that are not conjugated with folate and not cross-linked are cleared rapidly from the body. Higher accumulation in the spleen, liver, and kidneys was also observed for micelles with worm-like shapes compared to the spherical micelles. While the various factors of cross-linking, micelle shape, and conjugation with folic acid all contribute separately to prolong the circulation time of the micelle, optimization of these parameters for drug delivery devices could potentially overcome adverse effects such as liver and kidney toxicity.

Poly(aspartic acid)-based degradable assemblies for highly efficient gene delivery

Due to its good properties such as low cytotoxicity, degradability, and biocompatibility, poly(aspartic acid) (PAsp) is a good candidate for the development of new drug delivery systems. In this work, a series of new PAsp-based degradable supramolecular assemblies were prepared for effective gene therapy via the host-guest interactions between the cyclodextrin (CD)-cored PAsp-based polycations and the pendant benzene group-containing PAsp backbones. Such supramolecular assemblies exhibited good degradability, enhanced pDNA condensation ability, and low cytotoxicity. More importantly, the gene transfection efficiencies of supramolecular assemblies were much higher than those of CD-cored PAsp-based counterparts at various N/P ratios. In addition, the effective antitumor ability of assemblies was demonstrated with a suicide gene therapy system. The present study would provide a new means to produce degradable supramolecular drug delivery systems.

A surface-adaptive nanocarrier to prolong circulation time and enhance cellular uptake

Mixed-shell micelles (MSMs) with adaptive surfaces could rapidly and reversibly change surface properties to prolong circulation time and enhance cellular uptake.

Self-regulated multifunctional collaboration of targeted nanocarriers for enhanced tumor therapy

Exploring ideal nanocarriers for drug delivery systems has encountered unavoidable hurdles, especially the conflict between enhanced cellular uptake and prolonged blood circulation, which have determined the final efficacy of cancer therapy. Here, based on controlled self-assembly, surface structure variation in response to external environment was constructed toward overcoming the conflict. A novel micelle with mixed shell of hydrophilic poly(ethylene glycol) PEG and pH responsive hydrophobic poly(β-amino ester) (PAE) was designed through the self-assembly of diblock amphiphilic copolymers. To avoid the accelerated clearance from blood circulation caused by the surface exposed targeting group c(RGDfK), here c(RGDfK) was conjugated to the hydrophobic PAE and hidden in the shell of PEG at pH 7.4. At tumor pH, charge conversion occurred, and c(RGDfK) stretched out of the shell, leading to facilitated cellular internalization according to the HepG2 cell uptake experiments. Meanwhile, the heterogeneous surface structure endowed the micelle with prolonged blood circulation. With the self-regulated multifunctional collaborated properties of enhanced cellular uptake and prolonged blood circulation, successful inhibition of tumor growth was achieved from the demonstration in a tumor-bearing mice model. This novel nanocarrier could be a promising candidate in future clinical experiments.